Manafort had come under increasing pressure for his ties to a pro-Russia party in Ukraine and his work as a lobbyist.

"This morning Paul Manafort offered, and I accepted, his resignation from the campaign," Trump said in a statement.

"I am very appreciative for his great work in helping to get us where we are today, and in particular his work guiding us through the delegate and convention process. Paul is a true professional and I wish him the greatest success," Trump added.

Manafort told Trump he was becoming a distraction and he wanted to end that.

Manafort was also dogged by reports about secretive efforts he made to help the former pro-Russian government in Ukraine, where he worked on and off for several years.

He had also been viewed with trepidation by Jared Kushner, Trump's son-in-law and a major force within the campaign, the New York Times reported.

Earlier this week, Trump turned to Bannon to head the floundering campaign and named veteran pollster Kellyanne Conway as campaign manager.

With just under three months to go until Election Day, Manafort's departure reflects the shifting power centres of the Trump campaign.

It's the second high profile departure from the top of Trump's campaign structure after campaign manager Corey Lewandowski left the operation earlier this summer.